Magnetic detonator



United States Patent G MAGNETIC DE'IONATOR Howard E. Tatel, Washington, D.C., assignor to the United States of America as represented by the Secretary of the Navy Filed Feb. 7, 1946, Ser. No. 646,165

1 Claim. (Cl. 102-702) The present invention relates to magnetic detonators or impactors, of the type designed to be included in a fuze installed in an ordnance missile. The improved detonator, as a unitary part of the electrical fuze, is mounted adjacent the explosive charge of the missile, with its longitudinal axis substantially coincident with or parallel to the longitudinal axis of the missile.

In a fuze having the improved detonator an electrically energized primer is initially short-circuited with respect to the electrical output circuit of the magnetic detonator by a frangible conductor and mechanical detents are employed to hold the operating parts in safety or unarmed condition. Centrifugal forces developed by the spinning missile in flight are utilized to retract the detents, and the frangible conductor is broken as a result of centrifugal force, thereby removing the short on the primer. An electromagnetic generator having a movable armature is utilized. on impact of the projectile with its target, electrically to fire the squib.

In the accompanying drawings- Fig. 1 is a detailed sectional view of a preferred embodiment of detonator in accordance with the present invention taken on line 11 of Fig. 2 and showing the interior parts in unarmed position, the large arrow in Fig. 1 indicating the direction of flight of the projectile in which the detonator is installed;

Fig. 2 is a transverse sectional view on line 22 of Fig. 1;

Fig. 3 is a fragmentary detailed sectional view showing detents securing the armature in a safe position; and

Fig. 4 is a schematic diagram showing an initially short-circuited primer coupled to the output circuit of the generator.

The detonator is enclosed within a cylindrical metal casing 11, and includes an electrically energized primer 12 which is embedded in the front face of a molded plastic body 13, which is located within the casing 11, the front of the casing being closed by a metal plate 14.

The wires from the primer are passed around and anchored on two pairs of posts 15-15 and 16-16, which are embeded in the body, and from posts 1616 the separate wires extend rearwardly through exterior grooves 17-17 and within the casing to the winding of an electromagnetic generator which fills the rear end of the casing.

The generator includes a soft steel yoke 18 having a transverse exterior groove 19 to accommodate the wires from the squib. An annular groove is provided in the plate for a coil or winding 20. The armature 21 is a small circularly magnetized disk consisting, for example, of Alnico which covers the coil and clings to the yoke, as shown. The yoke and armature thus constitute a closed magnetic circuit. The armature is located in a round lCe recess 22 of ample size to permit separation of the armature from the yoke 18.

The armature is mechanically held in unarmed position, and in close contact with the yoke, by four balls 23 each pressed inwardly along a cam groove 25 in the rear face of the body 13 by an individual radial spring 24.

As best seen in Fig. 2 a fine work-hardened and frangible copper wire 26 is soldered to the two posts 1515 to bridge a gap between the posts and thus short circuit the primer. This wire 26 passes neatly through a hole 27 in a radially arranged slide-block 28, mounted to slide in a radial groove 29 provided therefor in the front portion of the body 13.

The block 28 is held in unarmed position by means of a slide-bolt 30 which is pressed forward by a spring 31 to overlap the slide-block and impinge against a stop pin 32 mounted in the block. The slide-bolt slides through an opening in a wall portion 33 of the body 13, which forms a stop for the bolt, after the latter is retracted.

'In Fig. 1 the detonater is shown in unarmed position. When the projectile is fired from a gun, due to set-back forces then developed, the slide-bolt 30 is retracted to release the initially detained slide-block 28. Centrifugal force of the spinning projectile throws out the released slide-block 28 thereby breaking Wire 26; and the same force retracts the detent-balls 23 from their positions in front of the armature.

Upon impact of the projectile against its target, armature 21 is projected away from the yoke, thereby decreasing the number of magnetic flux lines in the coil, and the resultant voltage therein induced causes an electrical surge current in the primer and detonation of the projectile.

What is claimed is:

A magnetic detonator for an ordnance missile, and comprising a yoke of magnetic material, a winding carried by said yoke, an armature coacting with said yoke to form therewith a normally closed magnetic circuit, with its magnetic flux interlinked with said winding, means mechanically holding the armature in contact with the yoke, said means being retractable by centrifugal force to release the armature and thus arm the detonator when spin occurs, said armature thereupon being held to the yoke solely by their mutual magnetic attraction, the surface of contact between the armature and the yoke being so oriented with respect to the direction of travel of the missile that upon impact inertial forces will cause the armature and yoke to separate suddenly, thereby generating a voltage in the winding, an electrically operable primer forming a circuit with the winding, means initially shortcircuiting the primer, means for breaking said short circuit including a member mounted to shift radially with respect to the missile, and means normally preventing such shift but movable by inertia when set-back occurs, to release the member, whereupon centrifugal force will cause the radial shift to take place, thereby breaking the short circuit when spin occurs.

References Cited in the file of this patent UNITED STATES PATENTS 809,885 Abendroth Ian. 9, 1906 FOREIGN PATENTS 1,089 Great Britain Jan. 13, 1912 149,723 Austria May 25, 1937 91,592 Sweden Feb. 24, 1938 525,333 Great Britain Aug. 27, 1940 

